In a device and a method for the determining local geometrical variations that have occurred in data, the data comprise a reference pattern X. The method comprises, for example, the following steps: modeling the local geometrical variations by means of an index variable J, said variable making it possible to place the samples of the distorted data in correspondence with those of the original data, estimating the local variations by using the reference pattern X included, a model of local distortion of the data and the distorted data.